Here's how to unlock the different endings:
Ending #1 "Beyond Time":
Deafeat Lavos after reviving Crono at Death Peak.
Ending #10 "Dino age":
Deafeat Lavos after facing Magus, but before facing Azala.
Ending #11 "What The Prophet Seeks":
Deafeat Lavos after facing Azala, but before Schala opens
the sealed door.
Ending #12 "Memory lane":
Deafeat Lavos after Schala opens the sealed door, but before
restoring the light to the pendant.
Ending #13 "Dream's Epilogue":
Defeat the Dream Devourer beyond Time's Eclipse
Ending #2 "Reunion":
Deafeat Lavos while Crono is dead.
Ending #3 "The Dream Project":
Deafeat Lavos in the Oceab Palace or immediately upon starting
a new game +.
Ending #4 "The successor of Guardia":
Deafeat Lavos after saving Leene and Marle, but before visiting
the End of Time.
Ending #5 "Good Night":
Deafeat Lavos after visiting the End of Time, but before returning
to the Middle ages.
Ending #6 "The Legendary Hero":
Deafeat Lavos after arriving in the middle ages, but before
obtaining the Hero's Badge.
Ending #7 "The Unknown Past":
Deafeat Lavos after obtaining the Hero's Badge, but before
the Gate key is stolen.
Ending #8 "People of the times":
Deafeat Lavos after regaining the gate jey, but before giving
the Masamune to Frog.
Ending #9 "The Oath":
Deafeat Lavos after giving the Masamune to Frog but before
New Dungeon: Dimensional Vortex
This new dungeon has three parts to it and can only be unlocked
when you've completed the game by defeating Lavos at the end of Black
Dimensional Vortex: Beat the game by taking the Black Omen path.
Defeat Lavos and obtain any of the 12 original endings.
The Lost Sanctum is one of the new bonus dungeons added to the
DS. In order to unlock this, you must unlock the Black Omen in 12,000
B.C. The Lost Sanctum will apear in 65 Million BC, and 600 AD in
Infinite Strength Capsules
When on the black omen, you will come across a Blubber Hulk
(which at first looks like a tornado on the ground). Approach it and
have Ayla use Charm which gives you the strength capsule. Run away and
go back through the door you came through (with the two Nus) and
Go to Guardia Forest in 600 AD. Once inside, take the first right
and go to the upper path. While in the small clearing, you'll notice a
bush in the upper left. Go next to the bush and it will begin to
shake. Press A and a monster will pop out, leaving a Shelter as he
runs away. Get the Shelter, and then leave the forest and reenter. Do
this until you have as many shelters as you want.